A mutated version of the delta variant that has caused panic in the UK has been detected in several states in the US, the CDC revealed this week.
AY.4.2, a subtype of the highly transmissible delta variant which has become informally known as "delta plus", accounted for 6% of all sequenced samples of the virus. Its emergence has coincided with a rebound in COVID cases in the UK.
To be sure, right now, the strain is still rare in the US and accounts for "well below 0.05%" of cases sequenced, the CDC says. So there's no reason to panic.
"At this time, there is no evidence that the sublineage AY.4.2 impacts the effectiveness of our current vaccines or therapeutics," the CDC said. "Vaccination remains the best public health measure to slow the spread of the virus and reduce the likelihood of new variants to emerge."
Around 16,830 AY.4.2 cases have been detected around the world across at least 28 countries, according to data from Outbreak.Info.
Jeffrey Barrett, director of the COVID-19 Genomics Initiative at the Wellcome Sanger Institute in the U.K., told Newsweek on Thursday that it's still unclear whether the subtype is helping drive rising case numbers in the UK.
"We are one of the groups that has observed a [roughy] 10 percent growth advantage compared to other Delta."
"I'd say we can't say for sure yet that that is a true biological advantage, as opposed to a bit of epidemiological 'luck' for this lineage, but the data are now accumulating week-by-week in favor of a small growth advantage."
While the sub-lineage is spreading in the U.K., experts have said AY.4.2 is not necessarily going to outcompete the original Delta variant.
Although AY.4.2 is being monitored in the UK, it hasn't yet been classified as a "variant under investigation" or a "variant of concern" by the WHO.